Strengthened CO ₂ -to-CO Electroreduction from Low-Concentration CO ₂ Streams via the Phosphorus Heteroatoms-Regulated Electronic Structure of a Single Atomic FeN ₄ Catalyst

Single atomic Fe catalysts have demonstrated excellent activity for pure CO₂ electroreduction (CO₂RR). However, designing a highly active catalyst for efficient CO₂RR from streams with diluted CO₂ concentration remains a significant challenge. Herein, P atoms were introduced into the second coordination shell of FeN₄ (FeN₄P), forming Fe-N-P bonds to facilitate the CO₂-to-CO conversion in an aqueous solution. The incorporation of P atoms enhanced both the activity and selectivity toward CO, reaching a maximum CO Faradaic efficiency (FE_CO) of 96.2 ± 0.5% at a current density exceeding -200 mA cm^-2 in 0.5 M KHCO₃. Moreover, the superior activity was further demonstrated by the 80.5 ± 2.3 and 61.5 ± 1.3% FE_CO at optimized conditions from streams containing only 15 and 5% CO₂, respectively. In situ characterizations reveal that the asymmetric FeN₄P structure enhanced the kinetics of adsorbed CO₂ reduction. Density functional theory calculation revealed that the electron-enriched FeN₄ center, modulated by the adjacent P atom, facilitated CO₂ adsorption and activation and lowered the energy barrier for *COOH formation, thereby promoting CO₂-to-CO conversion.